HowTo for blocky with docker and IPv6 necessary

[ikarisan]

Hi!

I am running docker as a docker container (via docker-compose) and it took me many days to figure out, how to enable IPv6 traffic to and from blocky. At first I didn't notice it, but after configuring IPv6 upstream servers I kept getting error messages that the IPv6 address could not be bound/used. Then I found out that IPv6 and docker are not really best friends. Below is how I got blocky, docker and IPv6 working for me.

1. Enable IPv6 for docker in daemon.json. Assuming that you are using docker 20.10.x, your daemon.json should look like this:

{
  "ipv6": true,
  "fixed-cidr-v6": "fdxx:xxx:xxx:xxx::/64",
  "experimental": true,
  "ip6tables": true
}

Please chose an indivdual fd::: address.

2. Create a new fd:::/64 network. You can use https://simpledns.plus/private-ipv6 for that.

3. For blocky add a new network to docker. Let's name it "ipv6net_1".

docker network create --driver bridge --ipv6 --subnet fd01:4c51:244f:5697::/64 --subnet 172.30.0.0/24 ipv6net_1 --attachable

Please use your personal IPv6/IPv4 subnet!

4. Create a docker-compose file that consideres this network. The following is an example. Please modify the values for your needs!

version: '3.9'
services:
  blocky:
    image: 'spx01/blocky'    
    pull_policy: always
    container_name: blocky
    restart: unless-stopped
    networks:
      ipv6net_1:
        ipv6_address: fd01:4c51:244f:f697::42
    sysctls:
      - net.ipv6.conf.all.disable_ipv6=0
    dns:
      - 10.10.0.1
      - 1.1.1.1
      - 8.8.8.8
    ports:
      - '53:53/tcp'
      - '4000:4000/tcp'
      - '53:53/udp'
    environment:
      - TZ=Europe/Berlin
    volumes: 
      - '/etc/docker_configs/blocky/config.yml:/app/config.yml'
      - 'blocky_logs:/logs'
    healthcheck:
      disable: true            
networks:
  ipv6net_1:
    external: true
    
volumes:
    blocky_logs:
      external: true

A "docker-compose up" should give you a blocky container with working outbound IPv6 traffic. :)

[0xERR0R]

Thanks for sharing!
Another option would be the usage of host network in Docker.

Also important: check if your clients get the correct ipv6 address of your machine where blocky runs. I use Fritzbox with DHCP as router. There are different settings necessary to set the ipv4 and ipv6 addresses which must be pushed to the client.

[ikarisan]

Thanks for sharing! Another option would be the usage of host network in Docker.

I tried to use the host network, but the outbound traffic did not work.

Also important: check if your clients get the correct ipv6 address of your machine where blocky runs. I use Fritzbox with DHCP as router. There are different settings necessary to set the ipv4 and ipv6 addresses which must be pushed to the client.

That's right. I use the docker host (Raspberry Pi) for DHCPv4 and the FritzBox for IPv6.
These are my IPv6 setting:

[x] Router Advertisement for LAN
--[x] Assign Unique Local Addresses (ULA) as long as there is no IPv6 internet connection

[x] Allow IPv6 prefixes, announced by other IPv6 router
[x] This FritzBox provides the default internet connection
--[x] High router advertisement preference

But I have to admit that IPv6 is still way too complex for me. I miss the simple control I have within an IPv4 network.